The regulation of interferon induction and synthesis will be studied in human cell strains stimulated with polyinosinic-polytidylic acid (poly I poly C) or Newscastle disease virus. We shall analyze the conditions leading to leukocyte (Le) or fibroblast (F) interferon production in these cell strains, including the effect of cell type, the type and dose of inducer, influence of metabolic inhibitors. The presence of biologically active mRNA specific for Le and F interferon in human fibroblast cell strains will be studied by injection of Xenopus laevis oocytes. Attempts will be made to separate the two interferon mRNA activities by physical and immunological techniques. Conditions for optimal interferon production will be studied in cultures of fresh human T lymphocytes stimulated with specific antigens or plant mitogens (e.g., phytohemagglutinin). Interferon produced in antigen- or mitogen-stimulated lymphocytes (T interferon) is distinctly different from both Le and F interferon. Once good methods for the production of T interferon are available we shall attempt to obtain biologically active mRNA specific for this interferon.